This invention relates in general to drive train assemblies for transferring rotational power from a source of rotational power to a rotatably driven device. In particular, this invention relates to an improved method for rotatably balancing a driveshaft adapted for use in a vehicular drive train assembly for transferring rotational power from an engine/transmission assembly to an axle assembly.
In most land vehicles in use today, a drive train assembly is provided for transmitting rotational power from an output shaft of an engine/transmission assembly to an input shaft of an axle assembly so as to rotatably drive one or more wheels of the vehicle. To accomplish this, a typical vehicular drive train assembly includes a hollow cylindrical driveshaft tube. A first universal joint is connected between the output shaft of the engine/transmission assembly and a first end of the driveshaft tube, while a second universal joint is connected between a second end of the driveshaft tube and the input shaft of the axle assembly. The universal joints provide a rotational driving connection from the output shaft of the engine/transmission assembly through the driveshaft tube to the input shaft of the axle assembly, while accommodating a limited amount of angular misalignment between the rotational axes of these three shafts.
Ideally, the driveshaft tube would be formed in the shape of a cylinder that is absolutely round, absolutely straight, and has an absolutely uniform wall thickness. Such a perfectly shaped driveshaft tube would be precisely balanced for rotation and, therefore, would not generate any undesirable noise or vibration during use. In actual practice, however, the driveshaft tubes usually contain variations in roundness, straightness, and wall thickness that result in minor imbalances when rotated at high speeds. To prevent such imbalances from generating undesirable noise or vibration, therefore, it is commonplace to counteract such imbalances by securing balance weights to selected portions of the driveshaft tube. The balance weights are sized and positioned to counterbalance the imbalances of the driveshaft tube such that it is balanced for rotation during use.
Traditionally, driveshaft tubes have been formed from steel or other metallic materials having relatively high melting temperatures. In such driveshaft tubes, welding has been commonly used to secure the balance weights thereto. More recently, however, driveshaft tubes have been formed from aluminum alloys and other metallic materials that are not well suited for welding, particularly in the high volume quantities usually associated with the vehicular manufacturing industry. Also, driveshaft tubes have recently been formed from composites and other materials that are not suited at all for welding.
To balance driveshaft tubes formed from these alternative materials, it has been proposed to use adhesive to secure the balance weights to the driveshaft tubes. Although adhesives are known that provide sufficient strength and durability to retain the balance weights on the driveshaft tube in the rugged environment of a vehicular drive train assembly, the use of such adhesives has not gain widespread acceptance. One of the reasons for this lack of acceptance is that the curing time for such adhesives is relatively long. As a result, an undesirably long time delay is usually encountered between the initial point in time at which the balance weight is applied to the driveshaft and the subsequent point in time at which the adhesive has cured to allow the driveshaft and balance weight assembly to be re-tested to confirm the achievement of proper balance. This undesirably long time delay prevents the efficient manufacture of the driveshaft tubes in the high volume quantities usually associated with the vehicular manufacturing industry. Thus, it would be desirable to provide an improved method for rotatably balancing a driveshaft adapted for use in a vehicular drive train assembly for transferring rotational power from an engine/transmission assembly to an axle assembly.
This invention relates to an improved method for rotatably balancing a driveshaft adapted for use in a vehicular drive train assembly for transferring rotational power from an engine/transmission assembly to an axle assembly. Initially, a conventional balancing apparatus is used to determined the size and location of the balance weights needed to properly balance the driveshaft. The determined location on the driveshaft is then cleaned so as to remove any contaminants therefrom. Next, an adhesive material is applied to either or both of the driveshaft and the balance weight. The adhesive material may, for example, be a multi-cure adhesive material including an adhesive portion and a curing activator portion. The balance weight is preferably formed having an inner surface that is curved to conform with the curvature of the outer surface of the driveshaft. The preferred balance weight is further formed having a serrated outer peripheral surface defined by a plurality of radially outwardly extending teeth and having a generally hat-shaped cross section including a relatively thick central portion and a relatively thin outer rim portion. The overall size of the balance weight may be varied to provide differing amounts of weight for facilitating the balancing process. A sufficient quantity of adhesive material is provided between the driveshaft and the balance weight such that when the balance weight is pressed against the driveshaft, at least a portion of the adhesive material is extruded outwardly into contact with at least a portion of the outer peripheral surface of the balance weight. The extruded portion of the adhesive material is then exposed to an accelerated curing process, such as ultraviolet radiation, heat, and the like, so as to cure at least that portion of the adhesive material to temporarily secure the balance weight to the driveshaft, thereby allowing the driveshaft to be immediately re-tested on the balancing apparatus to confirm that proper rotational balance has been achieved. The uncured first portion of the adhesive material located between the driveshaft and the balance weight will later cure without the use of any accelerated curing process to permanently secure the balance weight to the driveshaft.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.